BPhase change on reflection

We know that reflected light undergo a phase shift of π in EXTERNAL REFLECTION but there is no phase shift in INTERNAL REFLECTION . Does this violate Stokes Relation, which states that every reflected beam undergo of phase shift of π ?

True. But it clashes with what I have studied in Interference in Dielectric Films :

(1.) Phase changes by π in external reflection (i.e. reflection in rarer medium when the reflected ray bounces off the boundary of a denser medium).

(2.) Phase changes by 0 (i.e. NO PHASE CHANGE) in internal reflection (i.e. reflection in denser medium when the reflected ray bounces off the boundary of a rarer medium).

(3.) No phase change in any of refraction.

According to Stokes Relation, point (2.) should be false but according to Interference in Dielectric Films, it should be correct.

We can't argue with what you've learned about dielectric films. (I assume you were getting the right story!) so I guess you need to look at what it actually implied by this time reversal notion with rays. Time reversing involves two incident beams, which need to be the same as the emerging beams. Could that be what you are ignoring when you reckon you've found a flaw? My problem is that it all seems OK to me - but that could just be because I haven't thought deeply enough about it.